Stress induced connecting assembly

ABSTRACT

A connecting assembly is disclosed having a first component defining an opening, a second component adapted to be retained together with the first component and a connector component made of a superelastic alloy. Relative motion between at least two of the components causes a super-elastic activation of the connector wherein the activation simultaneously retains the components together with the connector interposed jointly therebetween. Preferably the connector component is pre-assembled to one of the first and second components. More preferably, the first component is pre-assembled with the connector and the second component is moved relative to the pre-assembled components to activate the superelastic alloy of the connector. Alternatively, the second component is pre-assembled with the connector and the first component is moved relative to the pre-assembled components to activate the superelastic alloy of the connector. In another alternative assembly, the first and second components are pre-assembled and relative motion occurs between the connector and the pre-assembled components.

Related Applications

[0001] This application is a continuation in part of Ser. No.09/311,938, filed May 14, 1999.

TECHNICAL FIELD

[0002] The present invention relates generally to metallic connectors,that is, devices that join together multiple parts by means of anintervening member, particularly connectors having one or more elementsmade of material that possesses super-elastic properties. The presentconnectors are suitable for high-performance industrial and medicalapplications involving different ranges of operating temperatures andcomponent materials being connected.

Background

[0003] The present inventor has previously filed application Ser. No.09/311,938 entitled “Stress Induced Seal” on May 14, 1999, Ser. No.09/440,064 entitled “Stress Induced Gasket” on Nov. 15, 1999 and Ser.No. 09/501,109 entitled “Stress Induced fastener” on Feb. 9, 2000, theentire disclosures of which are expressly incorporated by referenceherein and relied upon.

[0004] The use of metallic super-elastic alloys, such as Ni-Ti (nitinol)and other bi- or tri-metal alloys, has been documented in a variety oftechnical applications, including fasteners, connectors, gaskets, clampsand seals. Many such uses have required temperature in order to activatethe material and change its physical state, while others have usedmechanical forces that impart stress to cause a super-elastic physicaldeformation in the material. Of particular concern to the instantinventor is the application of the super-elastic material to connectors.The use of non-corrosive, metallic super-elastic material offers adecided advantage in high performance connecting assemblies, versus moreconventional connectors requiring threaded fasteners, springs, clamps orother holding or securing mechanisms. Particularly it can withstand morewear than alloys used in conventional connectors due to its hardersurface characteristics. It can also withstand extreme vibrations andnot loosen due its elastic pre-loaded condition without usingconventional adhesives to hold the assembled components and/or theconnector itself together. Adhesives used with conventional connectorsmake them very difficult to disassemble, whereas it is generallypossible to make a super-elastic connector completely reversible.

[0005] U.S. Pat. Nos. 5,395,193 and 5,584,631 to Krumme et al.., discussthe use of nickel-titanium shape memory retainers in an optimizedelastic condition that have super-elastic or pseudo-elastic properties.These fasteners are said to be useful for eyeglass assembly; they areplaced onto a pin to retain components together. However, this use doesnot contemplate an interposed connector.

[0006] U.S. Pat. No. 5, 683,404 to Johnson, entitled “Clamp and Methodfor its Use” further discusses shape memory materials that are“pseudo-elastic”, defining these materials in terms of their ability toexhibit super-elastic/pseudo-elastic recovery characteristics at roomtemperature. Such materials are said to deform from an austeniticcrystal structure to a stress-induced structure postulated to bemartensitic in nature, returning thence to the austenitic state when thestress is removed. The alternate crystal structures described give thealloy super-elastic or pseudo-elastic properties. Poisson's Ratio fornitinol is about 0.3, but this ratio significantly increases up toapproximately 0.5 or more when the shape memory alloy is stretchedbeyond its initial elastic limit. It is at this point thatstress-induced martensite is said to occur, i.e., the point beyond whichthe material is permanently deformed and thus incapable of returning toits initial austenitic shape. A special tool is employed by Johnson toimpart an external stretching force that deforms the material whichforce is then released to cause the material to return to its originalcondition. While the device is stretched, a member is captured by it andsecurely clamped when the stretching force is released. This device isintended for use in clamping and does not contemplate traditionalconnecting operations of the kind addressed by the present invention.Another use envisioned by Johnson is in connecting the modularcomponents of a medical device, as described in his U.S. Pat. No.5,858,020, by subjecting a thimble component made of shape memorymaterial to an external stretching stimulus to elongate and therebyreduce its transverse dimension. Upon release of the stretching force,this component returns towards its original rest dimension, contactingand imparting a force on another component. This is a sequentialstretching and relaxation of the super-elastic material rather than asimultaneous activation and retention operation. Also, specialstructures are necessary on the thimble to allow the stretching force tobe imparted.

[0007] In U.S. Pat. No. 5,197,720 to Renz, et al., a work piece is heldwithin a clamping tool by an expansion element made of shape memorymaterial that is activated by mechanical force. In this way, torque istransmitted through the shape memory member. This device is useful forbringing parts together for holding the work piece in order to performan operation. It does not, however contemplate a use as a connector.U.S. Pat. No. 5,190,546 to Jervis discloses insertion into a broken bonecavity of a split member made of shape memory material using asuper-elastic alloy. The split member holds the walls of the bone cavitywhen radial compressive forces acting on it are released In order forthe radial compressive force to reduce the diameter, the component mustbe split, allowing the reduction in dimension for insertion. It does notact as an interposed member in a connecting assembly.

[0008] Others have sought to utilize the properties of shape memorymaterials as locking, connector and bearing elements, e. g., U.S. Pat.Nos. 5,507,826 to Besselink, et al., 5,779,281 to Kapgan, et al., and5,067,827 to Arnold, respectively; however, such approaches haverequired temperature to be applied during use. U.S. Pat. Nos. 5,277,435to Kramer, et al. and 5,876,434 to Flomenblit, et al. similarly hasrelied upon temperature to activate the shape memory effect. Suchdependence on extrinsic activation by temperature introduces an addedprocess step and may further be disadvantageous in certain otherapplications.

[0009] U.S. Pat. No. 5,842,312 to Krumme, et al., entitled, “HystereticDamping Apparati and Methods”, employs shape memory tension elements toprovide energy dissipation. Such elements can be placed between buildingstructures, etc., which are subject to vibration, serving to absorb theenergy created by their relative movement. However, this patent does notcontemplate the vibration dampening effect of a super-elastic materialin the formation of a connector.

[0010] Accordingly, there is a need to form a connecting assembly usinga durable metallic, non-corrosive connector assembly, which are simpleto install using relative motion to activate the assembly.

[0011] There is a further need to form a secure connection betweencomponents that minimizes the micro-motional wear characteristics of theassembly, enhancing its useful life.

[0012] There is another need to form a fastened assembly that does notrequire temperature for its activation.

[0013] There is still a need to form an assembly using a fastener thatadjusts for differences in thermal coefficients of expansion orcontraction of dissimilar materials comprising those components beingfastened.

[0014] There is still a further need for a connector with elasticproperties that allow more forgiving tolerances during manufacturing ofthe assembly components.

Summary of Invention

[0015] According to an embodiment of the present invention, a connectingassembly has a first component defining an opening, a second componentadapted to be retained together with the first component and a connectorcomponent made of a superelastic alloy. Relative motion between at leasttwo of the components causes a super-elastic activation of the connectorwherein the activation simultaneously retains the components togetherwith the connector interposed jointly therebetween.

[0016] In a preferred embodiment of the present invention, the connectorcomponent is pre-assembled to one of the first and second components.More preferably, the first component is pre-assembled with the connectorthe second component is moved relative to the pre-assembled componentsto activate the superelastic alloy of the connector. Alternatively, thesecond component is preassembled with the connector and the firstcomponent is moved relative to the pre-assembled components to activatethe superelastic alloy of the connector.

[0017] In another preferred embodiment, the first and second componentsare pre-assembled and relative motion occurs between the connector andthe pre-assembled components.

[0018] In yet another embodiment of the present invention, the openingdefines an axis and relative motion occurs along the axis;alternatively, the relative motion could occur normal to the axis.

[0019] In still another embodiment of the present invention, thecomponents are rigidly retained.

[0020] In still yet another embodiment of the present invention, theconnection forms a seal.

[0021] An advantage of an embodiment of the present invention is that asuper-elastic alloy, e. g., nickel-titanium has an oxide layerpresenting a stronger wear surface than other traditional connectors.Moreover, the connector component is elastic in nature, allowing it toact as a vibration-dampening member that prevents the assembly fromloosening. Also, the components of the present assembly are moreforgiving of manufacturing tolerances. These connectors are entirelyreversible.

[0022] Another advantage of an embodiment of the present invention isthat a connection is effected by simple relative motion, not requiringthreaded fasteners, springs, clamps or other holding or securingmechanisms. This feature allows the connectors to be operable in a muchsmaller working space, further avoiding the complexity associated withtraditional connection devices.

[0023] A further advantage of an embodiment of the present invention isthat the super-elastic properties are not dependent on temperature toimpart the activaton force required to effect such a connection.

[0024] Other objects and advantages will be appreciated by those skilledin the art, by resort to the appended Drawings having reference numeralsthat correspond to the ensuing Description of one or more embodiments ofthe invention wherein the following Figures are further elucidated

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is an exploded external side view of a ball and asuper-elastic component (i.e., a washer), shown prior to assembly,illustrating the super-elastic effect operative in the presentinvention;

[0026]FIG. 2 is a sequential view of FIG. 1, showing the ball fullyengaged with the washer to form a connection;

[0027]FIG. 3 is a further sequential view of FIG. 2, showing the ballpushed entirely through the washer;

[0028]FIG. 4A is a top plan view of the washer of FIG. 3;

[0029]FIG. 4B is a top plan view of an alternative, open sided washer;

[0030]FIG. 5 is side view of a connector assembly of the inventionshowing a first component with an opening, a second component in theform of a ball, and a connector component (shown in phantom) in the formof a washer, prior to assembly;

[0031]FIG. 6 is a sequential view of FIG. 5 showing the componentsassembled (shown partially in phantom);

[0032]FIG. 7 is a side view of a connecting assembly similar to thatshown in FIG. 5 with an alternative second component in the form of apin;

[0033]FIG. 8 is a side view of a connecting assembly of the presentinvention, prior to activation by an external force, showing a firstcomponent with a collet activating a pre-assembled connector component(washer shown in phantom) to retain the second component (i.e., pinpartially shown in phantom);

[0034]FIG. 9 is a sequential view of FIG. 8 showing the componentsretained together upon activation of connector component (shown inphantom) by an external force applied to the collet;

[0035]FIG. 10 is a perspective view of an open sided connecting assemblyof the present invention, showing a first component and a connectorcomponent pre-assembled prior to activation of the connector by a secondcomponent i. e., ball;

[0036]FIG. 11 is a sequential front view of FIG. 10 showing thecomponents retained together upon activation of the connector (shown inphantom) by relative motion of the ball;

[0037]FIG. 12 is a side view of FIG. 11;

[0038]FIG. 13 shows a perspective view of a connecting assembly of thepresent invention with a first component (body) preassembled with asecond component (pin) prior to activation of multiple connectorcomponents (tubes) to retain the preassembled components;

[0039]FIG. 14 is a sequential top view of FIG. 13 showing the assemblywith its components connected; and

[0040]FIG. 15 is a cross sectional view taken substantially along lines15-15 of FIG. 14, showing deformation of the super-elastic connectortubes.

DETAILED DESCRIPTION OF THE DRAWINGS

[0041] Referring to FIGS. 1-3, the operative super-elastic propertiesemployed by the present inventor are illustrated. In FIGS. 4A-4B,alternative super-elastic washers used in an experimental assembly aregenerally shown at 10. The remaining FIGS. 5-15 depict preferredembodiments of a connecting assembly of the instant invention.

[0042] Referring again to FIGS. 1-3, a first component of assembly 10 isa ball 12 defining a given spherical shape with a cross sectionaldiameter having a first dimension D1. A second component consists ofwasher 14 defining a second given shape, in this case annular, having across section which is continuous with at least a second dimension D2sized with interference to the first dimension D1. One of the first 12and second 14 components, i. e., washer 14 in FIGS. 1-3, includes anopening 16 with an entrance edge or lip 18 that is sized to correspondto its associated continuous cross-section, i.e., the inner diameter D2.In FIG. 2, relative motion indicated by arrow 13 of ball 12 with firstdimension D1 causes it to contact the second dimension D2 of washer 14,imparting a force to super-elastically expand the second dimension,allowing the ball and washer to be jointly retained with one another.

[0043] Referring still to FIGS. 1-3 first dimension D1 is preferablygreater than second dimension D2 and the relative motion of the first 12and second 14 component causes the second dimension to expand. Althoughnot shown in these Figures, the assembly 10 may be provided with meansfor creating the relative motion 13; however, it is possible to impartthe necessary force to assemble the components 12, 14 using an externalsource, e. g., a mechanical press, lever or a clamp, etc.

[0044] Washer 14 is preferably an integral member made of asuper-elastic alloy, preferably nitinol, and more preferably SE508nitinol. This material is described in “Nitinol SE508 Data Sheet”, andis available from Nitinol Devices & Components, Inc., located inFremont, Calif. All of the super-elastic components referred to hereinpreferably are made of Nitinol SE508.

Experiment 1

[0045] Washer 12 of FIGS. 1-3 was placed in a mechanical clampingstructure (not shown) at room temperature prior to forming theexperimental assembly 10. Ball 12 was made of polished stainless steel,with a uniform spherical diameter D1 of 0.375 inches. The initialresting dimensions of washer 14 were as follows: inner diameterD2=0.360; outer diameter D3=0.550; thickness T1=0.050. Washer 14 wasplaced under the press with its axial movement constrained by a supportplate having an aperture (further not shown) underlying opening 16, theplate limiting the downward motion of the washer. Ball 12 was placed atthe entrance to opening 16 and the press engaged to move the balldownward, forcing it into the opening. The super-elastic material ofwasher 14 was activated by ball 12 in response to the expansion of itsinner diameter D2, by interference with the diameter D1 of the ball, upto a maximum insertion of the ball as shown in FIG. 2. The outerdiameter D3 of washer 14 was then measured with ball 12 thus insertedand it was observed to increase 0.014 inches to a new diameter D2 of0.564 inches. That is, the outer diameter D3 of washer 14 expanded 0.014inches, in nearly direct proportion to the difference between the balldiameter D1 and the inner diameter D2 of the washer. Neither thediameter D1 of ball 12 nor thickness T1 of washer 14 were observed tochange. Ball 12 was then pushed completely through the inner diameter D2of washer 12, whereupon the dimensions of the washer were measured asfollows: outer diameter D3=0.556; and inner diameter=0.367. Therefore,some of the deformation was of a “plastic” nature, that is, thedimensions of washer 14 were permanently altered. Because thesuper-elastic material was in the austenitic state, there was no returnto the extent of such plastic deformation. The 1-2% stated elasticcapacity was thus exceeded, and so the plastic deformation ensued to theextent it was beyond this elastic capacity. In order to verify theresults observed above, I repeated this experiment with a differentwasher having substantially the same dimensions and observed similarresults.

Experiment 2

[0046] The same ball 12 and washer 14 from the initial run of Experiment1 was used to form the assembly 10. I postulated that the maximumplastic deformation had already occurred and, thus, would not furtherchange. It was expected that the washer 14 would preserve itssuper-elastic properties and continue to admit ball 12 into opening 16,therefore expanding the resting dimensions of the washer in the mannerobserved for the initial run of Experiment 1. I observed that the innerD2 and outer D3 diameters of washer 14 measurably expanded topractically the same dimensions as was observed before, not greater orless. When ball 12 was pushed through opening 16, the same dimensionswere observed as at the conclusion of the initial run of Experiment 1. Auniform band or swath 17 (FIG. 3) was observed upon passage of ball 12through washer 14 (FIG. 3), in the circumferential area of diameter D1corresponding to its contact with the super-elastic material of theinner diameter D2. This indicates that an even seal was effectivelyformed in a substantial area surrounding the circumference of ball 12,rather than a narrow line of contact. Thus it is concluded that thesuper-elastic material deformed in response to the stress-activated sealformation by the relative motion, conforming to the contour of ball 12.With further reference to FIGS. 1-3, either of the first 12 and second14 components the experimental assembly 10 had a tapered lead tofacilitate activation of the super-elastic alloy. Lip 18 of opening 16may have a chamfered entrance edge (not shown), functioning as a lead-inthat makes easier the insertion of the first dimension D1 into thesecond dimension D2.

[0047] Returning to FIG. 4B and with reference to FIGS. 10-12, aconnector component in the form of an alternative washer is shown at 314with an opening 316. This washer 314 is configured for use in theconnector assembly generally shown at 310 as will be described below.

[0048] In FIGS. 5-6, a connection assembly is generally shown at 110. Aball 112 and a washer 114 are similar to those shown by FIGS. 1-3,except they are activated within a third component represented by a body120 having an opening consisting of a through-bore 121 with acounter-bore 122 within which the washer is placed. Washer 114 has anopening 116. Through-bore 121 has a central axis A which, preferably,also passes through the center of opening 116. The ball 112 is moved inthe direction indicated by arrow 113 along axis A, that is, relativeaxial motion, into opening 116 (FIG. 6) inducing an internal stress inthe connector causing opening 116 to super-elastically expand in thedirection of diverging arrows 124. Likewise the outer diameter D3expands to engage and form a connection against counter-bore 122.Because the outer diameter of washer D3, when engaged with counter-bore122, exerts an inward radial force shown by arrows 126, the innerdiameter D2 further contracts and exerts additional force on ball 112.Fig. 7 is similar to Figs.5-6 but for the substitution of pin 111 forball 112.

[0049] The components can be connected in various ways either bypre-assembling two of the components as shown in FIGS. 8 and 10 thenassembling these with the third in a final assembly as in FIGS. 9 and11-12. Tolerances can be chosen, as will be appreciated by those skilledin the art, so that there is an initial interference fit betweencomponents so that they can be temporarily held together in preparationfor the final assembly. Alternatively, the tolerances could be chosen sothat, while in the pre-assembled state, the components are looselyplaced into position in preparation for final assembly as shown in FIGS.5-7 and 13-15.

[0050] In FIGS. 8-9, a connecting assembly is generally shown at 210with a first component in the form of a body 220 including a collet 219.A second component in the form of pin 211 and a connector component inthe form of a washer 214 are provided, similar to those shown in FIG. 7.Body 220 has an opening consisting of a bore 221 with a counter-bore 222within which washer 214 is placed. Similar to FIGS. 1-7, washer 214 hasan opening 216. Bore 221 has a central axis A which, preferably, alsopasses through the center of opening 216. Pin 211 is pre-assembled in aloose-fitting relationship within opening 216. Collet 219 is radiallycompressed in the direction indicated by arrow 213 along axis A, thatis, relative motion is in a direction normal to axis A thereby inducingan internal stress in connector 214 causing opening 116 tosuper-elastically contract effecting the connection. Various means couldbe employed to radially compress collet 219 in a direction normal toaxis A, e. g., a slidably adjustable sleeve, etc., as will beappreciated by those skilled in the art It is to be understood that theterm “relative motion” encompasses the axial motion described inconjunction with FIGS. 1-7, as well as the radial compression of collet219 in FIGS. 8-9 which results in motion of the collet in a directionnormal to axis A relative to bore 221.

[0051] In FIGS. 10-12, a connecting assembly is generally shown at 310.A connector component represented by a washer 314, is pre-assembled witha first component represented by a body 320. Body 320 has an openingconsisting of an open through-bore 321 with a groove 323 within whichthe washer 314 is placed. Washer 314 has an opening 316. Through-bore321 has a central axis A which, preferably, also passes through thecenter of opening 316. A ball 312 is moved in the direction indicated byarrow 313 along axis A, that is, relative axial motion, into opening316. Alternatively ball 312 can be moved in a direction indicated byarrow 315 normal to axis A, into the opening 316. As ball 312 enterswasher opening 316, it induces an internal stress in washer 314, causingthe opening to super-elastically expand engaging the groove 323effecting a connection. Body 320 preferably has a base 324 and a shaft326 projecting therefrom.

[0052] In FIGS. 13-15, a connecting assembly is generally shown at 410.A first component body 420 has a through bore 421 defining an axis A. Asecond component shown as a pin 411 is pre-assembled within the bore 421in a loosely fitting relationship. Connector component represented by atleast one, preferably a pair of pegs 414, are aligned with through holes428 in the body 420. The through holes 428 run normal to axis A and passpartially into the through bore 421. The pegs 414 are inserted in thedirection of arrows 405 into the through holes 428 in the body 420. Asthe pegs 414 are inserted in an interposed relationship to the body 420and the pin 411 a super-elastic response is induced in the pegs 414effecting a connection. In an alternative the pegs 414 can beper-assembled in the through holes 428 in the body 420. Then, the pin411 is moved axially within the through bore 421 bringing it intocontact with the pegs 414 effecting a connection.

[0053] While one or more preferred embodiments of the present inventionhave been described, it should be understood that various changes,adaptations and modifications may be made without departing from thespirit of the invention and the scope of the appended Claims.

1. A connecting assembly comprising, a first component defining anopening, a second component adapted to be retained together with thefirst component, and a connector component made of a superelastic alloy,whereupon relative motion between at least two of the components causesa super-elastic activation in the connector, the activationsimultaneously retaining the components together with the connectorinterposed jointly there between.
 2. The assembly of claim 1 wherein therelative motion occurs between the first and second component.
 3. Theassembly of claim 1 wherein two of the components are pre-assembled. 4.The assembly of claim 1 wherein the relative motion occurs between theconnector component and the first and second components.
 5. The assemblyof claim 1 wherein the opening further defines an axis.
 6. The assemblyof claim 5 wherein the relative motion occurs along the axis.
 7. Theassembly of claim 5 wherein the relative motion occurs normal to theaxis.
 8. The assembly of claim 1 further comprising a rigid connection.9. The connector of claim 1 further comprising a seal.
 10. The connectorof claim 1 wherein the super-elastic alloy is nitinol.
 11. The connectorof claim 1 , wherein the super-elastic properties are exhibited withinthe operating temperature range of the assembly.
 12. A connectingassembly comprising, a first component defining an opening, a secondcomponent adapted to be retained together with the first component, anda connector component made of a superelastic alloy, pre-assembted withthe first component, whereupon relative motion between the first andsecond components causes the second component to induce a super-elasticactivation of the connector, the activation simultaneously retaining thecomponents together with the connector interposed jointly there between.13. The assembly of claim 12 wherein the opening further defines anaxis.
 14. The assembly of claim 13 wherein the relative motion occursalong the axis.
 15. The assembly of claim 13 wherein the relative motionoccurs normal to the axis.
 16. The assembly of claim 12 furthercomprising a rigid connection.
 17. A connecting assembly comprising, afirst component defining an opening, a second component adapted to beretained together with the first component, and a connector componentmade of a superelastic alloy, preassembled with the second component,whereupon relative motion between the first and second components causesthe first component to induce a super-elastic activation of theconnector, the activation simultaneously retaining the componentstogether with the connector interposed jointly there between.
 18. Theassembly of claim 17 wherein the opening further defines an axis. 19.The assembly of claim 18 wherein the relative motion occurs along theaxis.
 20. The assembly of claim 18 wherein the relative motion occursnormal to the axis.
 21. The assembly of claim 17 further comprising arigid connection.
 22. A connecting assembly comprising, a firstcomponent defining an opening, a second component adapted to be retainedtogether with the first component, and a connector component made of asuperelastic alloy, whereupon motion of the connector relative to thefirst and second components causes a superelastic activation in theconnector, the activation simultaneously retaining the componentstogether with the connector interposed jointly there between.
 23. Theassembly of claim 22 wherein the opening further defines an axis. 24.The assembly of claim 23 wherein the relative motion occurs along theaxis.
 25. The assembly of claim 23 wherein the relative motion occursnormal to the axis.
 26. The assembly of claim 22 further comprises twoconnectors.